Effect of upflowing field-aligned electron beams on the electron cyclotron waves in the auroral magnetosphere |
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| Authors: | Sushil Kumar S K Singh A K Gwal |
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| Institution: | (1) Physics Division, School of Engineering and Physics, The University of the South Pacific, Suva, Fiji;(2) Space Physics Laboratory, Department of Physics, Barkatullah University, Bhopal, 462 026, India |
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| Abstract: | The role of low density upflowing field-aligned electron beams (FEBs) on the growth rate of the electron cyclotron waves at
the frequencies ω
r < Ωe, propagating downward in the direction of the Earth’s magnetic field, has been analysed in the auroral region at ω
e/Ωe < 1 where ω
e is the plasma frequency and Ωe is the gyrofrequency. The FEBs with low to high energy (E
b) but with low temperature (T
‖b) have no effect on these waves. The FEBs with E
b < 1 keV and T
‖b (> 1.5 keV) have been found to have significant effect on the growth rate. Analysis has revealed that it is mainly the T
‖b which inhibits the growth rate (magnitude) and the range of frequency (bandwidth) of the instability mainly in the higher
frequency spectrum. The inhibition in the growth rate and bandwidth increases with increase in T
‖b. The FEBs with less E
b (giving drift velocity) reduce growth rate more than the beams with larger E
b. The inhibition of growth rate increases with the increase in the ratio ω
e/Ωe indicating that the beams are more effective at higher altitudes.
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| Keywords: | Field-aligned electron beams electron cyclotron waves wave-particle interaction auroral region |
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